What is mean by delegate? Why we need it? [duplicate]

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Delegates, can't get my head around them

Hi friends,

What is mean by delegate in objective C? Why we need it? When should we use it? Is there any types in it? How to use it?

Please friends, use simple words and examples to explain. I saw so many articles, forums.. But still i 开发者_如何转开发can not catch the exact explanation of it..

Thank you

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A delegate is a way to modify the behavior of a class without requiring the class to be subclassed. Often you don't want to dramatically change behavior, but tweak it a bit; subclassing would be overkill, so that's where delegates come in to play.

Look at it this way: a teenager represents a class, and her parent the delegate. The teenager's friend calls her to come hang out at the mall, but the teenager has to ask her parents if it's okay first. The parent -- the delegate -- can say yes or no. That's how delegates work in Cocoa.

Is there any types in it?

Delegates can generally be of any type. In 10.6, many delegates implement protocols with optional methods, so you'll see types like id <BlahClassDelegate>, but that wasn't common before 10.6.